A device of this kind is disclosed in U.S. Pat. No. 5,089,232.
The known apparatus is a chip-shaped reagent carrier for several channels which are lined with a colorimetric indicator. The indicator enters into a chemical coloring reaction in the presence of a gaseous and/or vaporous component of the gas mixture which is to be detected. The length of the coloration or the speed with which the coloration advances along the reaction zone is a measure of the quantity or concentration of the component to be detected. The evaluation of each coloration zone takes place in that a row of light sources emit visible or invisible light toward the reaction zone and the reflected light is reflected onto corresponding detectors. The light sources are arranged one behind the other. The signal transmitting unit as well as the signal receiving unit must be adapted to the course of the reaction zone such that a uniform irradiation of the channel path is possible. Only ,small quantities of color indicators are available for the colorimetric display because of the small dimensions of the channels and the reaction zones. The evaluation signal for the receiving unit is correspondingly small. More specifically, the measuring signal is correspondingly susceptible to disturbance components which are caused, for example, by a nonuniform distribution of the indicator material. Likewise, a nonuniform illumination of the reaction zone can lead to a falsification of the measuring signal.
The known carrier with its plurality of channel-shaped reaction zones is introduced into an evaluation unit with the aid of an automatic transport device for the purpose of carrying out a measurement. A data field is read out (for example, in the form of a bar code) during the insertion into the evaluation unit. The data field contains all data necessary for the measurement and evaluation of the measuring signals. The type and number of the reaction zones as well as the correlation which prevails for each reaction zone is provided in a coded form in the data field. The correlation is between the coloration length and concentration of the gaseous components to be detected. The data read in in this manner is transmitted to a control unit and a data processing device (microprocessor). The carrier is placed into a measuring position after evaluation of the data field. In this measuring position, one or more reaction zones are connected to a pump. With the aid of this pump, the gas component to be investigated is pumped through the channel-shaped reaction zones. The reaction zone used for the investigation is brought into the radiation region of the signal transmitting unit and the signal receiving unit for measuring the colorimetric coloration. The transmitting and receiving units are the same which had read out the data field in the evaluation position of the carrier. The indicator colors during the throughflow of the reaction channel in dependence upon the quantity of the gas component to be investigated. The coloration path is detected from the portion of the non-colored reaction zone by the reflection and/or the absorption of different wavelength intensities by the signal receiving unit.